Does Annulus Fibrosus Lamellar Adhesion Testing Require Preconditioning?

Area of Science:

• Biomechanical engineering
• Tissue mechanics
• Spine research

Background:

• The interlamellar matrix (ILM) resists delamination in the intervertebral disc (IVD).
• Understanding ILM mechanical properties is crucial for assessing disc injury risk.
• The viscoelastic nature of the ILM may necessitate preconditioning before mechanical testing.

Purpose of the Study:

• To optimize mechanical testing protocols for the ILM.
• To investigate the effect of preconditioning on ILM stiffness and strength.
• To determine if preconditioning is required before adhesive peel testing of the ILM.

Main Methods:

• Eighty-eight porcine cervical disc annular samples were tested.
• Samples were randomized into four groups: no preconditioning, or preconditioning at 0.01, 0.1, or 1 mm/s strain rate.
• Preconditioning involved ten cycles of 15% strain, followed by a 180° adhesive peel test.

Main Results:

• Samples preconditioned at 0.01 mm/s showed significantly reduced stiffness compared to non-preconditioned samples (p=0.014).
• No other statistically significant differences in stiffness or strength were observed between groups.
• The study found no significant impact of preconditioning at tested rates on ILM mechanical properties.

Conclusions:

• Preconditioning may not be necessary for 180° adhesive peel tests of the ILM.
• If preconditioning is used, slow rates (0.01 mm/s) should be avoided due to potential negative effects on tissue properties.
• Further research may be needed to fully elucidate the role of preconditioning in IVD mechanical testing.